The prevalence of coronary artery disease is increasing in young adults. We evaluated the outcomes of different types of acute coronary syndrome in 917 patients undergoing coronary angiography aged <= 45 years. Male sex, smoking, dyslipidemia were the most important risk factors. ST-elevation myocardial infarction (STEMI; 54.8%) predominated. The STEMI patients had higher risk of hospital mortality (3.6% vs 0.6%;P= .004) and major adverse cardiac and cerebrovascular events (MACCE; 13.8% vs 3.3%;P< .001, hazard ratio [HR], 4.65; 95% CI, 2.45-8.82). Presentation heart rate, blood pressure, heart failure, shock, arrhythmia, ejection fraction (EF), diabetes, contrast-induced nephropathy (CIN), and elevated troponin were associated with hospital mortality and MACCE. But only heart failure (HR, 5.816; 95% CI, 2.254-15.008) and CIN (HR, 6.241; 95% CI, 2.340-16.641) were independent risk factors for hospital MACCE. There was no difference in long-term mortality between the 2 groups, but non-STEMI patients had higher risk for MACCE after 3 years (14.4% vs 9.9%,P= .033). Although shock (HR, 0.814; 95% CI, 0.699-0.930), Killip class >= 2 (HR, 0.121; 95% CI, 0.071-0.170), CIN (HR, 0.323; 95% CI, 0.265-0.380), and EF (HR, 0.917; 95% CI, 0.854-0.984) were independent predictors of hospital death, only EF was the independent predictor of long-term mortality (HR, 0.897; 95% CI, 0.852-0.944).